Pavement breaking drill



Nov. 13, 1962 A. R. HENRY PAVEMENT BREAKING DRILL 2 Sheets-Sheet 1 FiledJuly 6, 1959 INVENTOR. Alba/"f f? Herr/y BY v WA. W

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PAVEMENT BREAKING DRILL Filed July 6, 1959 2 Sheets-Sheet 2 14/06 l?- HE9.- 2 r awry 3,063,508 PAVEMENT BREAKING DRILL Albert R. Henry, 844Roach St., Salina, Kans. Filed July 6, 1959, Ser. No. 825,232 6 Claims.(Cl. 175-147) This invention relates to new and useful improvements inpavement breaking drills or hammers, and has particular reference todrills or hammers of the power-operated type. It pertains toimprovements over the device disclosed in my co-pending applicationSerial No. 716,129, now Patent 2,905,168, filed February 19, 1958, andentitled Pavement Breaking Drill.

My prior structure involved a drill of the general class describedhaving a heavy striker oscillatable in a housing to strike the upper endof a drill bit also carried by said housing to drive said bit againstand into the pavement or other material against which it is pressed, adrive member rotatably driven in a plane parallel to the movement of thestriker, and a novel means connecting the drive member to the striker.This connecting means, which formed the primary subject matter of myprior application, constituted a T-shaped connector having the uprightleg thereof pivoted rotatably on the drive member, which constituted acrank, and a pairvof opposed toggles each consisting of an upper linkpivoted to one end of the cross arm of the T-connector, and a lower linkpivoted to the upper link at one end and to the striker at its oppositeend. The two upper links were thus pivoted to the connector at spacedapart points, and the two lower links were likewise pivoted to thestriker on spaced apart axes. A compression spring was disposed betweenthe two upper links and tended to urge them apart whereby to urge thetwo lower links into an axially aligned relation at right angles to thedirection of striker travel. This was termed a neutral position,movement of the striker in either direction therefrom causingcompression of the spring, and the parts were so proportioned that thisneutral position occurred just before impact of the striker against thebit as the device was operated by rotation of the drive crank. Thisstructure possessed certain advantages. The spring cushioned the actionof the striker at all times, slowed the upstroke of the striker and inso doing stored potential energy therein, and delivered this potentialenergy in the form of added momentum to the striker during its downwardor operative stroke. Also, since the neutral position of the togglesoccurred substantially at the moment of impact, the reactive force ofthe blow was not transmitted back through the linkages to the drivemember and housing, and hence not to the arms and shoulders of theoperator. This protected many parts from shock damage and wear, andpermitted use with much less fatigue to the operator.

However, the structure above described had certain weaknesses. Forexample, since the toggle ends were attached on separate pivotal axeswhich were spaced apart, and since the drive crank of course had acircular motion, the two toggles were extended and retracted unequallyduring certain portions of each crank rotation. Due to this unequaltoggle action, the compression spring between the upper toggle links wasnot only alternately compressed and relaxed as desired, but also theends thereof were moved out of axial alignment, so that the spring wassubjected to lateral deflection or bending stresses. At the ordinarycrank speed of perhaps 1500- 2000 rpm, this lateral deflection causedrapid fatigue failure of the spring, necessitating frequent repair orreplacement. Also, the T-connector was subject to a certain degree ofrandom and uncontrolled oscillation about its connection to the drivecrank, and this not only further contributed to the'lateral deflectionof the spring, but

3,063,503 Patented Nov. 13, 1962 also produced a lack of equality of theaction of the toggles which caused a vibration or roughness inoperation. The present invention has as its principal object theelimination of these difficulties, which it accomplishes in the main byeliminating the independently movable connector between the toggles andthe crank, by pivoting the upper links to the crank coaxially with eachother, and by pivoting the lower links to the striker coaxially witheach other. Any one of these changes would reduce the diflicultiesrecited. Together they produce two toggles which can never be flexedunequally, but which are always disposed symmetrically with respect tothe plane containing their end pivots, regardless to their degree offlexing. Hence the ends of the spring cannot be misaligned, and thespring cannot be laterally deflected.

Other objects are simplicity and economy of construction, efliciency anddependability of operation, and freedom from excessive servicingrequirements.

With these objects in view, as well as other objects which will appearin the course of the specification, reference will be had to thedrawing, wherein:

FIG. 1 is a vertical sectional view through a pavement breaking drillembodying the present invention, with parts left in elevation and partsbroken away,

FIG. 2 is a sectional view taken on line II--II of FIG. 1, with partsleft in elevation and parts broken away,

FIGS. 3 and 4 are sectional views taken respectively on lines III-IIIand IVIV of FIG. 1, and

FIG. 5 is an enlarged sectional view taken on line V-V of FIG. 1.

Like reference numerals apply to similar parts throughout the severalviews, and the numeral 2 applies generally to a hollow housing having aback wall 4, side walls 6, a curved top wall 8, and a bottom wall 10.The front of said housing is normally closed by a cover plate 12 afiixedthereto by screws 14. Said housing is also provided at each side thereofwith an outwardly projecting handle 16 attached to side wall 6 by screws18, and by means of which the drill may be positioned and manipulatedduring use. A cylindrical tubular barrel 20 extends through a circularhole 22 formed in bottom housing wall 10, said barrel being providedwith an integral flange 24 which is rigidly secured to said bottom wallby screws 26. Said barrel extends well below housing 2, and alsoupwardly into said housing.

Barrel 2% has a cylindrical internal bore 28 from end to end, and aheavy cylindrical striker 30 is carried for vertical sliding movement inthe upper portion thereof. A drill chuck 32 of essentially tubular formis inserted slidably into the lower end of the barrel and retainedtherein by a pair of bolt studs 34 extending loosely through lugs 36 ofsaid chuck and threaded into said barrel. A compression spring 38 iscarried on each stud between lug 36 and a nut 40 threaded on said stud,whereby the chuck is retained yieldably in position. The chuck has aninternal bore 42 of hexagonal cross-sectional shape, being provided witha hardened, wear-resistant liner 44. A hexagonal drill bit 46 is carriedfor axial sliding movement in bore 42, said bit having an integralflange 48 which engages a shoulder 50 formed by the lower end of insert44. Said bit extends well below chuck 32 and is provided with anoperative point 52 of any desired design, and extends at its upper endabove chuck 32 into bore 28 of barrel 2%). The bit is retained looselyin the chuck by a lever 54 (see FIG. 2) pivoted by means of bolt 56between lugs 58 integral with the chuck. Said lever is provided with atooth 60 which projects inwardly to a point beneath bit flange 48,whereby to prevent withdrawal of the bit, and a handle 62 which may beoperated to withdraw tooth 66 from beneath flange 48 to permitwithdrawal of the bit. The lever is normally retained in its operativeposition by a detent pin 64 carried by the chuck and urged against thelever by a spring 66. Barrel 20 has a vent hole 68 formed therein justabove the chuck, whereby to prevent the formation of a vacuum orpressure within the barrel when the striker is reciprocated therein aswill be described.

In the upper portion of housing 2, above the upper end of barrel 20, adisc 70 constituting a crank arm is carried for rotation by a hollowshaft 72 which extends horizontally at right angles to the extended axisof barrel 2t), and

which is supported rotatably by ball bearings 74 in a tubular bushing 76 formed integrally with back wall 4 of the housing. Disc 70 has afiixedthereto a forwardly projecting crank pin 78 which is parallel to buteccentrically olfset from shaft 72. A counterweight 80 is formedintegrally with disc '70, at a point thereof diametrically opposite fromcrank pin 7 8.

A hydraulic motor 82 is provided with a flange 84 which is secured tothe housing wall 4 by screws 86 so as to cover the outer end of bushing'76. The output shaft 88 of said motor extends into hollow shaft 72, andthe two shafts are secured against relative rotation by a key 759.Hydraulic fluid is supplied to and from motor 82 by a pair of flexibleconduits 92 and 94, which it will be understood may be connectedoperably into the hydraulic system of an ordinary farm tractor, or toany other suitable source of fluid under pressure. It will be understoodalso that the motor may be provided with suitable control valving,operable by the user to control the motor. Such valving is not hereshown as it forms no part of the present invention.

Crank pin 72 is connected to striker 30 by a pair of opposed toggleseach indicated generally by the numeral 96. Each of said toggles, asbest shown in FIGS. 1 and 2, consists of an upper link 98, pivoted oncrank pin 78 by means of a needle bearing 100, and a lower link 102pivoted at one end to the lower end of link 98 by a pivot pin 104, andpivoted at its opposite end to striker 3% by means of a pivot pin 106,both of links 102 being attached to the single pivot pin 1%. Barrel 20has longitudinal slots 168 formed in the upper portion thereof to admitlinks 102, and said links project into a diametric slot 110 formed inthe upper end portion of the striker. A helical compression spring 112extends horizontally between toggle links 98 intermediate their ends.Each end of said spring is located by a boss 114 affixed to a pressureplate 116 welded to one of links Q8. Said spring urges links 98 awayfrom each other, whereby links 162 are urged to a position extendingsubstantially oppositely from each other, whenever the device is atrest. This may be termed a neutral" position, and occurs, as shown inFIG. 1, when crank pin 73 is in its lowermost position and striker 30 isjust above the upper end of bit 46. Whenever striker 3% moves eitherupwardly or downwardly from this neutral position relative to thetoggles, spring 112 must be compressed. Counterweight 8% serves tobalance at least partially the weight of the parts supported by crankpin 78, and hence to promote smoother operation with less vibration andwith less bucking of the drill in the operators hands.

The operation of the device is substantially as follows: Referring toFIG. 1, it will be seen that toggles 96 are disposed in their "neutraPpositions when lower toggle links 102 extend oppositely from strikerpivot 106 in linear alignment with each other. In this position uppertoggle links 98 are spaced apart a maximum distance, and movement of thestriker either upwardly or downwardly with respect to the toggles willcause links 98 to be drawn closer together to compress spring 112. Ascrank disc 70 is turned by hydraulic motor 82 from the position shown inFIG. 1, crank pin 78 carried by said disc of course moves alternatelyupwardly and downwardly, and acting through the toggles, causes striker3G to move upwardly and downwardly in barrel 20. During the upwardmovement of pin 7 3, the inertia of striker 30 causes it to lag behindthe actual elevation of pin 78, with the 4 7 result that toggles 96 arepartially extended and spring 112 is compressed, and will remaincompressed so long as its tension is balanced by the accelerative forceimparted to the toggles by pin 78, or until pin 78 rises approximatelyto the elevation of the axis of disc 70. As pin 78 then continues to thetop of its movement, its vertical acceleration is of course negative,with the result that spring 112 is allowed to recover, thereby causingretraction of toggles 96 and delivering an upward impulse to thestriker. This impulse adds to the upward momentum of the striker alreadyinduced by direct action of the toggles, so that as pivot 78 reaches totop of its travel and starts its downward movement, the strikercontinues upwardly by its own momentum, moving toggle links 102 abovetheir neutral position and again forcing links 98 inwardly to compressspring 112, whereby the kinetic energy of said striker is stored in saidspring as potential energy. The spring remains compressed duringdownward acceleration of pivot 78, or approximately until pivot 78 isagain lowered to the level of the axis of disc 70. At this time thestriker is being forced downwardly at the full maximum velocity of pivot78, and toggles 96 are folded to compress spring 112. As pivot 78 passesbelow the axis of disc 70 and its downward acceleration becomesnegative, spring 112 is allowed to recover, whereby itsenergy isreleased to deliver an added downward impulse to the striker. It will beseen in FIG. 1 that links 102 pass their neutral position at or justbefore pivot 8 reaches its lowermost position, and that at this time thestriker is just above the upper end of bit 46. The striker continuesdownwardly by its own momentum and strikes the bit which operates in theusual manner to drill into or break pavement or the like against whichit is rested.

Since the striker engages the bit at a time that spring 112 is eitherfully extended or only very slightly compressed, and toggles 96 aresubstantially at their neutral positions, it will be seen thatsubstantially the entire kinetic energy of the striker is available inthe blow to the bit. Also for the reason that the toggles aresubstantially neutral at the moment of impact, the impact of the blow,or more properly the reaction from the blow, will not be transmittedback through the toggle linkages to the housing. The drill is thusrendered smoother in operation and less fatiguing to the operator, inthat the tendency of the drill to jerk and buck in the operators handsis reduced.

The structure which has been described is similar to that disclosed inmy above identified prior application, except that in the priorstructure the upper toggle links 98, in place of being pivoted coaxiallyto pin 78, were pivoted respectively at spaced apart points to the endsof the cross arm of an inverted T-shaped connector, the upright leg ofwhich was in turn pivoted to a crank pin corresponding to crank pin 78in the present structure; and with the difference also that in the priorstructure the lower toggle links 192 were pivoted to the striker onhorizontally spaced apart axes, rather than coaxially as in the presentstructure. These three changes, namely pivoting the lower linkscoaxially to the striker, pivoting the upper links coaxially, and theelimination of the connector intermediate the upper links and the pin,constitute the improvements of the present invention.

With the upper links and the lower links pivoted respectively to thecrank and the striker on spaced apart axes, as in the prior structure,it will readily be apparent that due to the rotary motion of the crankpin the two toggles were flexed unequally at all times except at the topand bottom dead-center positions of the crank, and that the degree ofthis inequality was continuously changing at a high rate of speed. Forthis reason, the two ends of spring 112 were continuously being movedinto and out of axial alignment, thus subjecting the spring to a rapidor vibrating lateral or bending deflection. This resulted in a much lesssmooth operation than is obtainable with the present structure, andcaused rapid fatigue of the spring, necessitating frequent repair orreplacement thereof. Also, it was found that the connector between theupper links and the crank pin often oscillated about the crank pin in amore or less random and uncontrolled manner, which also createdroughness and vibration in operation, and increased the frequency andmagnitude of the lateral flexing to which the spring Was subjected. Anyone of the three changes enumerated above would partially correct thesedifficulties, the elimination of the intermediate connector preventingany uncontrolled movement of the upper toggle pivot, and making eitherthe upper toggle pivots or the lower toggle pivots coaxial tending toreduce any inequalities of flexing of the two toggles. With both theupper and lower toggle pivots coaxial, the two toggles must always besymmetrically disposed with respect to a plane including the axes ofcrank pin 78 and pivot pin 106, and hence the two toggles cannot beflexed unequally at any time. Hence the end mounting bosses 114 ofspring 112 cannot be moved out of alignment with each other, and thespring itself is hence never subjected to lateral bending. Thisstructure has been found to contribute substantially to the efi'iciencyof operation of the device, both in that the spring 112 is caused tohave a much longer eiTective life, and in that the mechanism operatesmuch more smoothly with less vibration, thereby providing operationwhich is considerably less tiring to the operator and in which the motorand toggle bearings are subjected to less wear.

While I have shown and described a specific embodiment of my invention,it will be readily apparent that many minor changes of structure andoperation could be made without departing from the spirit of theinvention as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. A pavement breaking drill comprising a housing, a tubular barrelfixed in said housing and extending downwardly therefrom, an elongateddrill bit carried for limited longitudinal sliding movement in saidbarrel and extending downwardly therefrom, a striker carried for slidingmovement in said barrel and operable to strike the upper end of saidbit, a drive member constituting a crank carried in the upper portion ofsaid housing in spaced relation above the upper end of said barrel, saidcrank being rotatable on an axis at right angles to the extended axis ofsaid barrel and including a crank pin disposed eccentrically to thecrank axis, means for rotating said crank, a pair of opposed toggleseach comprising an upper link and a lower link pivotally joined at theircontiguous ends, the opposite ends of said lower links being pivoted tosaid striker, connecting means pivotally joining the opposite ends ofsaid upper links together in coaxial relationship, said pivotalconnecting means being pivoted to said crank pin for rotation thereon,and a compression spring extending between and connected at its oppositeends respectively to said two upper links, whereby to urge said upperlinks away from each other.

2. The structure as recited in claim 1 wherein said pivotal connectingmeans is pivoted to said crank pin on an axis coaxial with the pivotalconnection of said upper toggle links to said connecting means.

3. The structure as recited in claim 1 wherein said upper toggle linksare pivotally mounted on said crank pin in coaxial relation with eachother.

4. A pavement breaking drill comprising a housing, a tubular barrelfixed in said housing and extending downwardly therefrom, an elongateddrill bit carried for limited longitudinal sliding movement in saidbarrel and extending downwardly therefrom, a striker carried for slidingmovement in said barrel and operable to strike the upper end of saidbit, a drive member constituting a crank carried in the upper portion ofsaid housing in spaced relation above the upper end of said barrel, saidcrank being rotatable on an axis at right angles to the extended axis ofsaid barrel and including a crank pin disposed eccentrically to thecrank axis, means for rotating said crank, a pair of opposed toggleseach comprising an upper link and a lower link pivotally joined at theircontiguous ends, the opposite ends of said lower links being pivotedcoaxially to said striker, connecting means pivotally joining theopposite ends of said upper toggle links to said crank pin, and acompression spring extending between and connected at its opposite endsrespectively to said two upper links.

5. The structure as recited in claim 4 wherein said connecting meansconnects said upper links for relative movement about a common axis, andis itself mounted pivotally on said crank pin.

6. The structure as recited in claim 4 wherein said connecting meansconnects said upper links for relative movement about a common axis, andis itself mounted pivotally on said crank pin, so that the axis of saidcrank pin coincides with the pivotal axis of saidupper links.

References Cited in the file of this patent UNITED STATES PATENTS513,326 Howard Jan. 23, 1894 619,048 Mayer e Feb. 7, 1899 655,028Sneller July 31, 1900 665,249 Mayer Jan. 1, 1901 883,024 Humpert Mar.24, 1908 1,089,104 Beck Mar. 3, 1914 1,401,317 Comstock Dec. 27, 19212,519,477 Kind Aug. 22, 1950

